There are two basic types of wheelchairs, motorized and manual driven. Manual wheelchairs have been well known for many years. Motorized wheelchairs provide the user with more mobility, especially if the user's arm muscles are too weak to drive the wheelchair in a manual mode. The most significant drawbacks of the motorized wheelchair are its weight and lack of portability. Someone who wants to travel with their motorized wheelchair needs a specially designed van and ramp system or lift system to get the motorized wheelchair into the vehicle. In addition, the motorized wheelchair needs a power source, such as a battery which is costly and adds logistic issues of recharging.
Due to the above-cited drawbacks, many individuals opt for a manual wheelchair. The manual wheelchair is lighter and is also less expensive. Another advantage is that a manual wheelchair can be folded, adding to its portability. Individuals who have some type of disability or injury, often still can drive by getting into their car, folding their wheelchair and putting it in their car. The most significant drawback of a manual wheelchair is that it is not easy to use on ramps or steep inclines. A wheelchair with a speed reducer gearing mechanism would aid this problem. U.S. Pat. No. 3,563,568, issued Feb. 16, 1971, to Reuben V. Sasse et al., shows a variable ratio rotary drive mechanism for a wheelchair and provides a basic two-speed wheelchair.
At present, there is a need for an improved and simplified mechanism for shifting such a multispeed wheelchair. The mechanism needs to be close to the user's hand so that it can be shifted with ease. Additionally, it would be desirable to have the ability to easily convert an existing wheelchair into a multispeed chair. This would minimize conversion costs because there would be no need to replace the entire wheelchair frame.
Active wheelchair users may find the need in running errands to take the wheels off of their wheelchair several times in one day. Many wheelchair users find it particularly convenient to have quick release, easily removable wheels. This allows more compact transport and storage of the wheelchair. When using a multispeed hub, it is necessary to transfer torque to the wheelchair frame when in a gear reduction mode. Being able to positively transfer this torque as well as conveniently shift between multiple speeds presents unique challenges if the wheel is to remain quickly releasable and retrofitable to existing wheelchairs without modification. The present inventors believe that these needs have not previously been addressed.